1. FIELD OF THE INVENTION
The present invention generally relates to locking devices and more particularly to an improvement in an electromagnetic door lock device:
2. PRIOR ART
Various types of door lock devices have been devised in the past. Certain of such devices are electromagnetic and a few of these employ an electromagnet connected to the top of a door frame and a movable armature connected to the top of a door in the frame. Difficulties with proper tolerances and clearances in use and with durability when and if an attempt is made to force the locked door open have resulted in an improvement in the form of the device claimed in U.S. Pat. No. 4,826,223 which utilizes a shear lock plate easily replaced if door forcing occurs and not an integral part of the electromagnet housing which otherwise would become damaged by such forcing. The plate allows some adjusting of spacing and tolerances.
However, there remains a need for a further improvement which will permit further door frame-door clearance while still permitting full operation of the device, in order to compensate for any door and/or frame irregularities. Such an improvement should be durable, efficient, inexpensive and capable of being utilized in a variety of forms.